(1) Field of the Invention
The invention relates to single-use cartridges for the storing and dispensing of dental two-component impression materials.
(2) Description of Related Art
Impression materials for taking dental impressions are commercially available as a combination of two components that are stored separately and mixed prior to use. The mixture hardens after a processing time on the order of minutes during which the material is filled into an impression tray at the dentist's followed by taking the impression in the mouth of the patient. The hardened impression is then removed and serves for fabrication of the model or is scanned in order to produce a virtual model.
Impression materials can be mixed in the dental office by stirring in manual mode or through the use of so-called automix devices. Mixing devices of this type for automatic mixing of dental impression materials are commercially available on the market, e.g. as models of the Pentamix® series made by 3M ESPE, Plug&Press® Dispenser made by Kettenbach, MixStar® made by DMG or Dynamix® made by Heraeus Kulzer.
There continues to be a need to improve said devices and systems with regard to their user comfort and the reliability and reproducibility of the process of taking an impression. It is desirable for the user to be able to fill impression trays easily and rapidly and to pre-select and/or vary the processing time in this context.
The inventors mainly pursued the goal to develop a system that allows impression materials to be mixed automatically by a device in the dental office and, in this context, have the processing time set variably by the user/dentist/assistant—as was previously possible only with hand-mixed and hand-dosed impression materials.
An additional requirement is the ease of handling, preferably for single use (single-use/single-dose) allowing the time needed for the entire process of preparing and filling the impression tray to be minimized. This time need includes everything that needs to be done in relation to filling the impression tray, including providing and dosing the material, assembly of components, and disposal of residual amounts as well as cleaning. In detail, these processes include the following
Hand- or motor-operated devices have become established in dental offices in the past few years that dose and convey impression materials from tubular bag systems or multi-chamber cartridges and at the same time mix them by means of static or rotating attachments. For complete filling of impression trays, it is customary to use motor-operated devices that are fitted with twin-cartridges or tubular bags with a capacity of 360 to 380 ml. These package sizes last for an average of 10 tray fillings. These devices are therefore used together with replaceable rotating mixing attachments that are intended for single use. Some of these attachments are quite laborious to connect to the device and/or cartridge.
For smaller amounts (e.g. for impression taking of prepared single teeth or correctable impressions), multi-use twin-cartridges with a capacity of 25 to 75 ml and replaceable static single-use mixers are used.
WO 2007/126532 and US 2007/0228076 describe multi-component cartridges and EP 1 846 308 describes multi-component syringes that contain clearly smaller amounts of 0.5 to 2.5 ml such that this amount, with a static mixer that is screwed on or plugged on, is sufficient for a single-use application with correctable impression material.
WO 2008/048603 describes pre-filled portion packages whose content is to be mixed by hand.
EP 1 308 137 A2 presents a mixing device that facilitates variable dosing of liquid components. The subject matter of DE 32 33 366 A1 is an apparatus that triggers the plungers of two cartridges separately such that the individual components can have different dispensing speeds.
However, the systems described above are associated with the following disadvantages:
The large-volume tubular bags and cartridges require correspondingly large and powerful machines which take up much working space in the office, which frequently is not available. Replacement of the cartridges and mixers is associated with time expenditure and soiling and/or contamination by the components of the product. Once a cartridge is fitted with the components, the filling levels of the two component chambers first need to be levelled by discarding some material that is conveyed from the device.
The paste mixture that is conveyed out always has a processing time that is determined by the material, but subject to the influence of ambient and/or storage temperature. This leads to large variations of the processing times of said mixtures depending on seasonal and climatic zone influences. To correct this problem, said materials are commercially available having different processing times settings, e.g. as regular set or fast set, or it is recommended to temperature-equilibrate them in the refrigerator or temperature-controlled cabinet.
Meanwhile many different rotating mixers have become established in the market, but are not mutually compatible in many cases or do not result in an optimal mixture for the consistency at hand. The user is therefore often forced to keep in stock multiple mixers that might later be confused.
Although cartridges for dispensing by means of hand-operated devices hold a volume of 40-50 ml on average which is sufficient for complete filling of one impression tray, they necessitate the use of very much force or expenditure of very much time. Kneadable consistencies cannot be conveyed by them at all. The climate and processing time issue mentioned above applies in this case in the same manner.
In older systems, for example those of the silicone impression materials that cross-link by means of condensation polymerization, the user can use under- or overdosing of the activator to individually control the processing time since the components of said materials are provided individually in tubes, cans or bottles. Neither of the cartridge, tubular bag, and syringe systems that are commercially available thus far can provide this advantage any longer due to their fixed dosage. However, the option of variable dosing is associated with disadvantages in that said materials can be dosed incorrectly or the mixing thereof is often poor or insufficient and requires adept users.